Rotating machines are very sensitive to mass unbalance which has a harmful effect on its running accuracy and service life. Therefore,a variety of dynamic balancing methods and devices are studied to reduce the vibrat...Rotating machines are very sensitive to mass unbalance which has a harmful effect on its running accuracy and service life. Therefore,a variety of dynamic balancing methods and devices are studied to reduce the vibration caused by mass unbalance. On-line active balancing is a new balancing procedure which is more convenient and precise than the previous methods. In this paper,an electromagnetic balancer based on ring coils and permanent magnets is presented. The balancer has a simple structure and the self-locking function without clutch,and transfers power by the non-contact electromagnetic field. In order to justify the rationality of its design,a two-dimension(2D) electromagnetic finite element model is conducted to verify that this magnetic circuit has no flux leakage and saturation. A three-dimension (3D) 1/10 model of the balancer is built to obtain the self-locking torque and driving torque. Based on the research work above,an electromagnetic balancer is developed. By testing the balancer using COCO80,it is verified effective to reduce the rotor unbalance at the speed of 1300 r/min.展开更多
Cloud computing is a collection of disparate resources or services,a web of massive infrastructures,which is aimed at achieving maximum utilization with higher availability at a minimized cost.One of the most attracti...Cloud computing is a collection of disparate resources or services,a web of massive infrastructures,which is aimed at achieving maximum utilization with higher availability at a minimized cost.One of the most attractive applications for cloud computing is the concept of distributed information processing.Security,privacy,energy saving,reliability and load balancing are the major challenges facing cloud computing and most information technology innovations.Load balancing is the process of redistributing workload among all nodes in a network;to improve resource utilization and job response time,while avoiding overloading some nodes when other nodes are underloaded or idle is a major challenge.Thus,this research aims to design a novel load balancing systems in a cloud computing environment.The research is based on the modification of the existing approaches,namely;particle swarm optimization(PSO),honeybee,and ant colony optimization(ACO)with mathematical expression to form a novel approach called PACOHONEYBEE.The experiments were conducted on response time and throughput.The results of the response time of honeybee,PSO,SASOS,round-robin,PSO-ACO,and P-ACOHONEYBEE are:2791,2780,2784,2767,2727,and 2599(ms)respectively.The outcome of throughput of honeybee,PSO,SASOS,round-robin,PSO-ACO,and P-ACOHONEYBEE are:7451,7425,7398,7357,7387 and 7482(bps)respectively.It is observed that P-ACOHONEYBEE approach produces the lowest response time,high throughput and overall improved performance for the 10 nodes.The research has helped in managing the imbalance drawback by maximizing throughput,and reducing response time with scalability and reliability.展开更多
The dynamic balancing is an important issue in mechanism design.For the existing balancing methods,both passive and active ones,there is still room for improvement in adaplability and independency.In view of this,a co...The dynamic balancing is an important issue in mechanism design.For the existing balancing methods,both passive and active ones,there is still room for improvement in adaplability and independency.In view of this,a concept of active balancer is developed as a new solution for the dynamic balancing with more flexibility.The proposed balancer is an independent additional device with a control system inside,which consists of a two-degree-of-freedom(DOF)linkage and a controllable motor,and can be attached to a machine expediently with little change to its original structure and motion.One of the two inputs of the two-DOF linkage shares the same shaft with its output,which is connected to the input shaft of a machine to be balanced and driven by the original actuator.The other input is driven by the control motor.By properly selecting the speed trajectories of the control motor and link parameters of the two-DOF linkage,one or more dynamic effects of the mechanisms can be minimized or eliminated adaptively.The design procedure of the active balancer is put forward and a two-step optimization is developed to find out optimal design parameters of the balancer for various design requirements and constraints.Taking a force-balanced crank-rocker mechanism as the reference mechanism,numerical examples are given to illustrate the design procedure.The balancing effects of the proposed balancer are compared with those of the existing adding dyads(DYAD)method.The results show that the introduction of the control system provides the active balancer with better balancing effect and more flexibility than the DYAD method.A considerable reduction in the dynamic effects(input torque,shaking moment and shaking force)can be achieved for different balancing object by designing the structural and control parameters of the balancer,and the deterioration of dynamic performance caused by alterative working conditions can be compensated effectively by redesigning the control parameters.展开更多
This paper presents an efficient model reduction technique for linear time-varying systems based on shifted Legendre polynomials.The approach constructs approximate low-rank decomposition factors of finite-time Gramia...This paper presents an efficient model reduction technique for linear time-varying systems based on shifted Legendre polynomials.The approach constructs approximate low-rank decomposition factors of finite-time Gramians directly from the expansion coefficients of impulse responses.Leveraging these factors,we develop two model reduction algorithms that integrate the low-rank square root method with dominant subspace projection.Our method is computationally efficient and flexible,requiring only a few matrix-vector operations and a singular value decomposition of a low-dimensional matrix,thereby avoiding the need to solve differential Lyapunov equations.Numerical experiments confirm the effectiveness of the proposed approach.展开更多
BACKGROUND:Hemiplegia,a prevalent stroke-related condition,is often studied for motor dysfunction;however,spasticity remains under-researched.Abnormal muscle tone significantly hinders hemiplegic patients’walking rec...BACKGROUND:Hemiplegia,a prevalent stroke-related condition,is often studied for motor dysfunction;however,spasticity remains under-researched.Abnormal muscle tone significantly hinders hemiplegic patients’walking recovery.OBJECTIVE:To determine whether early suspension-protected training with a personal assistant machine for stroke patients enhances walking ability and prevents muscle spasms.METHODS:Thirty-two early-stage stroke patients from Shenzhen University General Hospital and the China Rehabilitation Research Center were randomly assigned to the experimental group(n=16)and the control group(n=16).Both groups underwent 4 weeks of gait training under the suspension protection system for 30 minutes daily,5 days a week.The experimental group used the personal assistant machine during training.Three-dimensional gait analysis(using the Cortex motion capture system),Brunnstrom staging,Fugl-Meyer Assessment for lower limb motor function,Fugl-Meyer balance function,and the modified Ashworth Scale were evaluated within 1 week before the intervention and after 4 weeks of intervention.RESULTS AND CONCLUSION:After the 4-week intervention,all outcome measures showed significant changes in each group.The experimental group had a small but significant increase in the modified Ashworth Scale score(P<0.05,d=|0.15|),while the control group had a large significant increase(P<0.05,d=|1.48|).The experimental group demonstrated greater improvements in walking speed(16.5 to 38.44 cm/s,P<0.05,d=|4.01|),step frequency(46.44 to 64.94 steps/min,P<0.05,d=|2.32|),stride length(15.50 to 29.81 cm,P<0.05,d=|3.44|),and peak hip and knee flexion(d=|1.82|to|2.17|).After treatment,the experimental group showed significantly greater improvements than the control group in walking speed(38.44 vs.26.63 cm/s,P<0.05,d=|2.75|),stride length,peak hip and knee flexion(d=|1.31|to|1.45|),step frequency(64.94 vs.59.38 steps/min,P<0.05,d=|0.85|),and a reduced support phase(bilateral:24.31%vs.28.38%,P<0.05,d=|0.88|;non-paretic:66.19%vs.70.13%,P<0.05,d=|0.94|).For early hemiplegia,personal assistant machine-assisted gait training under the suspension protection system helps establish a correct gait pattern,prevents muscle spasms,and improves motor function.展开更多
This paper analyzes the load unbalance problem and voltage fluctuation problem in a 3-wire DC distribution system.It also analyzes a solution to these problems;a positive Buck-Boost voltage balancer is proposed and ex...This paper analyzes the load unbalance problem and voltage fluctuation problem in a 3-wire DC distribution system.It also analyzes a solution to these problems;a positive Buck-Boost voltage balancer is proposed and explored in order to fulfill the requirements of high quality power supply for the loads on its load side.Compared with the conventional balancer,a positive Buck-Boost converter is added to solve the voltage fluctuation problem,and the theories and methods of the voltage balancer are extended to analyze the working principle,derive the design equations,explore the stability,and calculate the efficiency.Both simulations and small power experiments are carried out to verify the validity of the working principle,the topology,and the control strategy.展开更多
LEO satellite communication systems have the characteristics of high-speed and periodic movement.The handover of user link occurs frequently,which has a serious impact on user terminal application and system capacity....LEO satellite communication systems have the characteristics of high-speed and periodic movement.The handover of user link occurs frequently,which has a serious impact on user terminal application and system capacity.To address this issue,we propose a handover strategy of LEO satellite user terminal based on multi-attribute and multi-point(MAMP)cooperation.Firstly,the satellite-user-time matrix is established by using the satellite constellation coverage and handover model.Then,combined with the visual time and signal quality,the user access matrix and satellite load matrix are extracted to determine the weight equation of the handover strategy with the channel reservation.According to the system modeling simulation,the algorithm improves the handover success rate by 2.5%,the lasted call access success rate by 3.2%,the load balancing degree by 20%,and the robustness by two orders of magnitude.展开更多
Hearing and balance disorders are significant health issues primarily caused by developmental defects or the irreversible loss of sensory hair cells(HCs).ldentifying the underlying genes involved in the morphogenesis ...Hearing and balance disorders are significant health issues primarily caused by developmental defects or the irreversible loss of sensory hair cells(HCs).ldentifying the underlying genes involved in the morphogenesis and development of HCs is crucial.Our current study highlights rhpn2,a member of rho-binding proteins,as essential for vestibular HC development.The rhpn2 gene is highly expressed in the crista and macula HCs.Loss of rhpn2 function in zebrafish reduces the otic vesicle area and vestibular HC number,accompanied by vestibular dysfunction.Shorter stereocilia and compromised mechanotransduction channel function are found in the crista HCs of rhpn2 mutants.Transcriptome RNA sequencing analysis predicts the potential interaction of rhpn2 with rhoab.Furthermore,co-immunoprecipitation confirms that Rhpn2 directly binds to RhoA,validating the interaction of the two proteins.rhpn2 knockout leads to a decreased expression of rock2b,a canonical RhoA signaling pathway gene.Treatment with the RhoA activator or exogenous rock2b mRNA injection mitigates crista HC stereocilia defects in rhpn2 mutants.This study uncovers the role of rhpn2 in vestibular HC development and stereocilia formation via mediating the RhoA signaling pathway,providing a target for the treatment of balance disorders.展开更多
An integral part of the effort to reduce greenhouse gas emissions is carbon footprint accounting.EPA categorizes facility carbon footprints in three scopes.Scope-2 emissions include electricity,heat or steam purchased...An integral part of the effort to reduce greenhouse gas emissions is carbon footprint accounting.EPA categorizes facility carbon footprints in three scopes.Scope-2 emissions include electricity,heat or steam purchased from a utility provider.This paper evaluates the existing calculation methods for scope-2 CO2 emissions for purchased electricity.The electricity grid in US is complex and is divided spatially into states,eGRID regions,balancing authorities(BAs),and utilities.Up to hourly temporal granularity can be obtained from available datasets.A matrix is developed that categorizes different datasets based on the complexity to calculate the carbon emission factors.Spatial and temporal variations are evaluated.There are significant spatial overlap between regions in different categories and emission factors within a region show sub-regional variation.An area analysis is done using zip-code polygons to determine whether a state or balancing authority is smaller for all the overlapping cases.Temporal variations in emission factors are significant depending on the balancing authority considered.A single method to calculate scope-2 emission factors may not be accurate and efficient in every case and a nuanced assessment of emission factors is warranted.An implementation pathway for a“smart carbon calculator”—one that gives accurate carbon footprint that is the spatially and temporally most granular is suggested.展开更多
Accurate water budget closure is critical for sustainable water resource management facing increased pressures from climate change and human activities.Although error reduction methods for individual water balance com...Accurate water budget closure is critical for sustainable water resource management facing increased pressures from climate change and human activities.Although error reduction methods for individual water balance components have advanced,persistent biases remain due to the independent development of datasets,impacting basin scale water budget balance.In this research,we analyzed the mathematical origin of the bias between water budget components and developed a new basin-scale water balance calibration method that redistributes errors across components while enforcing water balance constraints.Validation confirms systematic improvements,with reduced RMSE(Precipitation:-2.29 mm/month;ET:-1.34 mm/month)and increased R2 against in situ observations.Applied to the Jinghe River Basin(2000−2019),the calibrated data reveal declining precipitation(-1.70 mm/year)and evapotranspiration(-1.84 mm/year)alongside slightly increasing runoff(0.20 mm/year in basin depth),signaling a drying trend.Land cover changes—marked by cropland loss(-3,497 km^(2))and forest(+720 km^(2))and grassland(+2,776 km^(2))expansion—reflect improved water consumption requirements by ecosystem,raising concerns for water retention and ecosystem stability.The method is particularly effective for ungauged basins with sparse ground data and underscores the need for integrated land-water management to enhance long-term resilience.展开更多
This paper presents a programmable frequency scan algorithm based on harmonic balance.The core idea involves treating systems under perturbation as nonlinear time-periodic(NTP)systems.Steady-state harmonics are first ...This paper presents a programmable frequency scan algorithm based on harmonic balance.The core idea involves treating systems under perturbation as nonlinear time-periodic(NTP)systems.Steady-state harmonics are first solved via Newton-Raphson iteration through a set of nonlinear equations,and then input-output variables are selected to estimate the linear transfer function of the original NTP system without perturbations.The applications and insights of the proposed algorithm are discussed,particularly in guiding existing frequency scan algorithms,which are restricted by time-domain signal generation or measurement.This improvement is achieved through linear stability analysis of NTP systems with perturbations.展开更多
Tajikistan contains the majority of Central Asia’s glaciers,which cover about 6.00%of the national territory;their rapid shrinkage poses a significant threat to regional water resource security.However,glacier monito...Tajikistan contains the majority of Central Asia’s glaciers,which cover about 6.00%of the national territory;their rapid shrinkage poses a significant threat to regional water resource security.However,glacier monitoring in Tajikistan was interrupted after 1991,creating a substantial gap in understanding the current state and temporal evolution of these glaciers.Based on glacier inventory data,in situ measurements,and published literature,this study examined the present status and recent variations of glaciers in Tajikistan through data integration and validation,literature collation and comparative analysis,and the application of Geographic Information System(GIS)spatial analysis techniques.As of 2023,Tajikistan possesses a total of 11,528 glaciers,encompassing an area of 7624.48(±305.58)km2.Small glaciers dominate in number,whereas large glaciers account for the majority of the total area.Over the past two decades,the glacier count has decreased by 2014,and the total area has decreased by 628.98 km2,corresponding to an average annual reduction rate of 0.33%.Regional shrinkage rates range from 4.10%to 22.28%.Glaciers have undergone accelerated mass loss during the past 20 a;only those on the northeastern Pamir Plateau exhibit a weak positive mass balance.Observations of typical monitored glaciers also reveal intensified melting and retreat,consistent with regional trends.In light of the recent acceleration of glacier shrinkage in Tajikistan,focused measures should be implemented to strengthen glacier monitoring,enhance public awareness of glacier preservation,and promote the sustainable development and utilization of glacier tourism.These findings bridge the knowledge gap regarding the spatiotemporal dynamics of Tajikistan’s glaciers over recent decades and provide essential data support for regional water resource management.展开更多
Rubber-toughened thermoplastic materials have become ubiquitous in modern society owing to their lightweight nature and desirable combination of advantageous performances.Despite the ever-increasing demand,the develop...Rubber-toughened thermoplastic materials have become ubiquitous in modern society owing to their lightweight nature and desirable combination of advantageous performances.Despite the ever-increasing demand,the development of polymer alloys that are lightweight,high-strength,and high-toughness remains an ongoing challenge.Inspired by the unique“salami”microstructure from commercial acrylonitrile butadiene styrene copolymer(ABS)and high-impact polystyrene(HIPS),a facile approach was developed to overcome the trade-off between enhancing the toughness and rigidity of fully polymer-based alloys by virtue of elastomeric salami particles.This strategy entails pre-grafting rigid poly(lactic acid)(PLLA)chains with glycidyl methacrylate-grafted octene ethylene copolymer(POE-g-GMA)using complementary reactive groups.It can be envisaged that the PLLA grafts featuring strong incompatibility with polypropylene(PP)remain fixed in elastomer phase upon the subsequent melt compounding,facilitating the in situ formation of“hard core(PLLA)-soft shell(polyolefin elastomer,POE)”particles in polypropylene(PP)matrix.The all-polymer alloys containing elastomeric salami particles demonstrated unprecedented performance combinations,including upper notched impact strengths(56.8 kJ/m2),even higher tensile strength(36.8 MPa),and Young’s modulus(0.93 GPa)than that of the PP matrix.Furthermore,these materials are lightweight without the incorporation of reinforcing nano-fillers,which is competitive with industrial engineering plastics.It is highly anticipated that this universal and highly efficient protocol will be appropriate for arbitrary rubber toughened/reinforced systems,offering a paradigm in the design of advanced all-polymer alloys.展开更多
The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study pro...The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study provides more rigorous evidence supporting the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity(PV)inversion method.Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s^(–1) and 10 m s^(–1),we demonstrate that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component,characterized by vortex Rossby waves.Furthermore,the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core.As an air parcel undergoes cyclonic rotation,it ascends on the right side of the tilt vector,which increases relative humidity,leads to saturation,and drives the development of convective asymmetries,with maximum upward motion aligned with the tilt direction.This study suggests that the response of TC vortices to the environmental VWS involves complex interactions between vortex tilt,asymmetries in TC structure,and convection,all of which can largely be understood within the framework of balanced dynamics.展开更多
In-situ enlargement of super-large-span tunnels can intensify excavation-induced unloading in the surrounding rock,increasing deformation demand and failure risk during construction.This study combines laboratory mode...In-situ enlargement of super-large-span tunnels can intensify excavation-induced unloading in the surrounding rock,increasing deformation demand and failure risk during construction.This study combines laboratory model tests with FLAC3D simulations to evaluate the stabilizing role of prestressed anchor cables and to establish an energy-balance framework for support optimization.Comparative model tests of existing and enlarged tunnel sections,with and without anchors,show that reinforcement increases load-carrying capacity,reduces displacement,and confines damage to more localized zones.The numerical simulations reproduce displacement fields,shear-strain localization,and plastic-zone evolution with good agreement against the experimental observations.The energy framework is implemented in the in-situ simulations by quantifying unloading-related energy release in the rock mass and reinforcement work contributed by the anchors,and by introducing an energy release–reinforcement ratio as a stability indicator.Parametric analyses indicate that anchor length,spacing,and prestress influence stability in a nonlinear manner,with diminishing returns once reinforcement extends beyond the mechanically dominant deformation zone.An efficient parameter window is identified that improves deformation and yielding control while avoiding unnecessary reinforcement.The results provide an energy-consistent and design-oriented basis for prestressed anchorage selection in large-span tunnel expansion.展开更多
Energetic materials face critical challenges in balancing energy density and safety,driving the development of low-sensitivity high-energy materials.Though vital for modern defense and civilian applications,low-sensit...Energetic materials face critical challenges in balancing energy density and safety,driving the development of low-sensitivity high-energy materials.Though vital for modern defense and civilian applications,low-sensitivity high-energy materials remain scarce,with 1,3,5-trinitro-2,4,6-triaminobenzene as the only deployed example.Planar lamellar energetic crystals,which utilize weak interlamellarπ-πstacking for mechanical energy dissipation,have shown significant promise.However,their rational design is constrained by insufficient understanding of intermolecular interaction synergy.This review synthesizes the structural features of planar lamellar energetic crystals,emphasizing three core elements:the single-atomic-thickness planar stacking architecture,the"strong intralamellar and weak interlamellar interaction"paradigm(key to balancing energy density and safety for low-sensitivity high-energy materials,LSHEMs),and the role of molecular planarity in reducing shear slip barriers.It categorizes design strategies into two frameworks:H–bonding dominated(single-component:cross-shaped assembly,strong H–bonding in high symmetric molecules;multi-component methods:tenon-and-mortise,acceptor-donor separation)and other intermolecular interactions(e.g.,π-πstacking-drivenπ-π2max model,π-hole recognition).Case studies in single/multi-component crystals confirm that these strategies tune interaction synergy to achieve target packing motifs.The review highlights that interaction engineering is pivotal for PLEC design,offering a targeted theoretical framework for rational development of LSHEMs(to address the scarcity of practical LSHEMs)and guiding future crystal engineering for energy-safety balanced systems.展开更多
Objective:To analyze the improvement effect of early postoperative rehabilitation training on balance ability and quality of life in elderly patients with hip fracture.Methods:A total of 50 elderly patients with hip f...Objective:To analyze the improvement effect of early postoperative rehabilitation training on balance ability and quality of life in elderly patients with hip fracture.Methods:A total of 50 elderly patients with hip fracture admitted to our hospital from January 2023 to January 2024 were selected and divided into the observation group(25 cases)and the control group(25 cases)by random number table method.The control group received routine nursing,while the observation group received early rehabilitation training on the basis of routine nursing.The balance ability(Berg Balance Scale,BBS)and quality of life(SF-36)of the two groups were compared.Results:The BBS scores of the observation group at all postoperative time points were significantly higher than those of the control group(p<0.05),and the quality-of-life scores of the observation group were also significantly higher than those of the control group(p<0.05).Conclusion:Early postoperative rehabilitation training for elderly patients with hip fracture can improve their balance ability,enhance their quality of life,and reduce the incidence of postoperative complications,which is worthy of clinical promotion.展开更多
Quasi-periodic solutions with multiple base frequencies exhibit the feature of 2π-periodicity with respect to each of the hyper-time variables.However,it remains a challenge work,due to the lack of effective solution...Quasi-periodic solutions with multiple base frequencies exhibit the feature of 2π-periodicity with respect to each of the hyper-time variables.However,it remains a challenge work,due to the lack of effective solution methods,to solve and track the quasi-periodic solutions with multiple base frequencies until now.In this work,a multi-steps variable-coefficient formulation is proposed,which provides a unified framework to enable either harmonic balance method or collocation method or finite difference method to solve quasi-periodic solutions with multiple base frequencies.For this purpose,a method of alternating U and S domain is also developed to efficiently evaluate the nonlinear force terms.Furthermore,a new robust phase condition is presented for all of the three methods to make them track the quasi-periodic solutions with prior unknown multiple base frequencies,while the stability of the quasi-periodic solutions is assessed by mean of Lyapunov exponents.The feasibility of the constructed methods under the above framework is verified by application to three nonlinear systems.展开更多
Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects...Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects as nextgeneration microwave receivers.Linear gain and linear dynamic range(LDR)are critical metrics for assessing receiver sensitivity and demodulation fidelity,respectively.We numerically solve the four-level master equation and then employ particle swarm optimization(PSO)algorithm to co-optimize linear gain and LDR in atomic superheterodyne receivers based on balanced homodyne detection.Further,we systematically account for dominant dephasing mechanisms in the simulation,encompassing spontaneous decay,transit dephasing,collision dephasing,laser linewidth dephasing,and Doppler averaging.Homodyne readout utilizes both the real and imaginary parts of polarizability for sensing.In the case of the photon shot noise limit,its signal-to-noise ratio(SNR)expression resembles that of direct optical-intensity readout.However,the inherent coherent subtraction operation in homodyne detection significantly suppresses common-mode noise,while appropriately increasing the reference beam power enhances the gain in practical experiments.Indeed,this co-optimization problem,characterized by a high-dimensional variable space,two objectives,and non-convexity,is well-suited for solution by PSO.In addition,probe and coupling detuning contribute equivalently to polarizability and compensate for each other owing to Doppler averaging,thereby reducing the optimization variable space by one.By adopting a product form of linear gain and LDR as the fitness function,the PSO achieves rapid convergence.Here,the effectiveness of the PSO results is verified via the total harmonic distortion(THD).The relative error-based LDR calculation method we proposed efficiently measures receiver response linearity with consuming fewer computational resources.This research is expected to offer valuable insights into enhancing the performance of Rydberg-atom-based superheterodyne receivers.展开更多
基金The National Science and Technology Major Project of China(No.2010ZX04012-014)
文摘Rotating machines are very sensitive to mass unbalance which has a harmful effect on its running accuracy and service life. Therefore,a variety of dynamic balancing methods and devices are studied to reduce the vibration caused by mass unbalance. On-line active balancing is a new balancing procedure which is more convenient and precise than the previous methods. In this paper,an electromagnetic balancer based on ring coils and permanent magnets is presented. The balancer has a simple structure and the self-locking function without clutch,and transfers power by the non-contact electromagnetic field. In order to justify the rationality of its design,a two-dimension(2D) electromagnetic finite element model is conducted to verify that this magnetic circuit has no flux leakage and saturation. A three-dimension (3D) 1/10 model of the balancer is built to obtain the self-locking torque and driving torque. Based on the research work above,an electromagnetic balancer is developed. By testing the balancer using COCO80,it is verified effective to reduce the rotor unbalance at the speed of 1300 r/min.
基金Taif University Researchers are supporting project number(TURSP-2020/211),Taif University,Taif,Saudi Arabia.
文摘Cloud computing is a collection of disparate resources or services,a web of massive infrastructures,which is aimed at achieving maximum utilization with higher availability at a minimized cost.One of the most attractive applications for cloud computing is the concept of distributed information processing.Security,privacy,energy saving,reliability and load balancing are the major challenges facing cloud computing and most information technology innovations.Load balancing is the process of redistributing workload among all nodes in a network;to improve resource utilization and job response time,while avoiding overloading some nodes when other nodes are underloaded or idle is a major challenge.Thus,this research aims to design a novel load balancing systems in a cloud computing environment.The research is based on the modification of the existing approaches,namely;particle swarm optimization(PSO),honeybee,and ant colony optimization(ACO)with mathematical expression to form a novel approach called PACOHONEYBEE.The experiments were conducted on response time and throughput.The results of the response time of honeybee,PSO,SASOS,round-robin,PSO-ACO,and P-ACOHONEYBEE are:2791,2780,2784,2767,2727,and 2599(ms)respectively.The outcome of throughput of honeybee,PSO,SASOS,round-robin,PSO-ACO,and P-ACOHONEYBEE are:7451,7425,7398,7357,7387 and 7482(bps)respectively.It is observed that P-ACOHONEYBEE approach produces the lowest response time,high throughput and overall improved performance for the 10 nodes.The research has helped in managing the imbalance drawback by maximizing throughput,and reducing response time with scalability and reliability.
基金supported by National Natural Science Foundation of China(Grant No.50405004,50875018)Key Project of National Natural Science Foundation of China(Grant No.50335040)
文摘The dynamic balancing is an important issue in mechanism design.For the existing balancing methods,both passive and active ones,there is still room for improvement in adaplability and independency.In view of this,a concept of active balancer is developed as a new solution for the dynamic balancing with more flexibility.The proposed balancer is an independent additional device with a control system inside,which consists of a two-degree-of-freedom(DOF)linkage and a controllable motor,and can be attached to a machine expediently with little change to its original structure and motion.One of the two inputs of the two-DOF linkage shares the same shaft with its output,which is connected to the input shaft of a machine to be balanced and driven by the original actuator.The other input is driven by the control motor.By properly selecting the speed trajectories of the control motor and link parameters of the two-DOF linkage,one or more dynamic effects of the mechanisms can be minimized or eliminated adaptively.The design procedure of the active balancer is put forward and a two-step optimization is developed to find out optimal design parameters of the balancer for various design requirements and constraints.Taking a force-balanced crank-rocker mechanism as the reference mechanism,numerical examples are given to illustrate the design procedure.The balancing effects of the proposed balancer are compared with those of the existing adding dyads(DYAD)method.The results show that the introduction of the control system provides the active balancer with better balancing effect and more flexibility than the DYAD method.A considerable reduction in the dynamic effects(input torque,shaking moment and shaking force)can be achieved for different balancing object by designing the structural and control parameters of the balancer,and the deterioration of dynamic performance caused by alterative working conditions can be compensated effectively by redesigning the control parameters.
文摘This paper presents an efficient model reduction technique for linear time-varying systems based on shifted Legendre polynomials.The approach constructs approximate low-rank decomposition factors of finite-time Gramians directly from the expansion coefficients of impulse responses.Leveraging these factors,we develop two model reduction algorithms that integrate the low-rank square root method with dominant subspace projection.Our method is computationally efficient and flexible,requiring only a few matrix-vector operations and a singular value decomposition of a low-dimensional matrix,thereby avoiding the need to solve differential Lyapunov equations.Numerical experiments confirm the effectiveness of the proposed approach.
文摘BACKGROUND:Hemiplegia,a prevalent stroke-related condition,is often studied for motor dysfunction;however,spasticity remains under-researched.Abnormal muscle tone significantly hinders hemiplegic patients’walking recovery.OBJECTIVE:To determine whether early suspension-protected training with a personal assistant machine for stroke patients enhances walking ability and prevents muscle spasms.METHODS:Thirty-two early-stage stroke patients from Shenzhen University General Hospital and the China Rehabilitation Research Center were randomly assigned to the experimental group(n=16)and the control group(n=16).Both groups underwent 4 weeks of gait training under the suspension protection system for 30 minutes daily,5 days a week.The experimental group used the personal assistant machine during training.Three-dimensional gait analysis(using the Cortex motion capture system),Brunnstrom staging,Fugl-Meyer Assessment for lower limb motor function,Fugl-Meyer balance function,and the modified Ashworth Scale were evaluated within 1 week before the intervention and after 4 weeks of intervention.RESULTS AND CONCLUSION:After the 4-week intervention,all outcome measures showed significant changes in each group.The experimental group had a small but significant increase in the modified Ashworth Scale score(P<0.05,d=|0.15|),while the control group had a large significant increase(P<0.05,d=|1.48|).The experimental group demonstrated greater improvements in walking speed(16.5 to 38.44 cm/s,P<0.05,d=|4.01|),step frequency(46.44 to 64.94 steps/min,P<0.05,d=|2.32|),stride length(15.50 to 29.81 cm,P<0.05,d=|3.44|),and peak hip and knee flexion(d=|1.82|to|2.17|).After treatment,the experimental group showed significantly greater improvements than the control group in walking speed(38.44 vs.26.63 cm/s,P<0.05,d=|2.75|),stride length,peak hip and knee flexion(d=|1.31|to|1.45|),step frequency(64.94 vs.59.38 steps/min,P<0.05,d=|0.85|),and a reduced support phase(bilateral:24.31%vs.28.38%,P<0.05,d=|0.88|;non-paretic:66.19%vs.70.13%,P<0.05,d=|0.94|).For early hemiplegia,personal assistant machine-assisted gait training under the suspension protection system helps establish a correct gait pattern,prevents muscle spasms,and improves motor function.
基金supported in part by the National High Technology Research and Development of China("863 Program")(Grant No.2013AA050104)
文摘This paper analyzes the load unbalance problem and voltage fluctuation problem in a 3-wire DC distribution system.It also analyzes a solution to these problems;a positive Buck-Boost voltage balancer is proposed and explored in order to fulfill the requirements of high quality power supply for the loads on its load side.Compared with the conventional balancer,a positive Buck-Boost converter is added to solve the voltage fluctuation problem,and the theories and methods of the voltage balancer are extended to analyze the working principle,derive the design equations,explore the stability,and calculate the efficiency.Both simulations and small power experiments are carried out to verify the validity of the working principle,the topology,and the control strategy.
基金supported by the Innovation Funding of ICT,CAS under Grant(No.E261020)Jiangsu Key Research and Development Program of China(No.BE2021013-2)Zhejiang Key Research and Development Program(No.2021C01040).
文摘LEO satellite communication systems have the characteristics of high-speed and periodic movement.The handover of user link occurs frequently,which has a serious impact on user terminal application and system capacity.To address this issue,we propose a handover strategy of LEO satellite user terminal based on multi-attribute and multi-point(MAMP)cooperation.Firstly,the satellite-user-time matrix is established by using the satellite constellation coverage and handover model.Then,combined with the visual time and signal quality,the user access matrix and satellite load matrix are extracted to determine the weight equation of the handover strategy with the channel reservation.According to the system modeling simulation,the algorithm improves the handover success rate by 2.5%,the lasted call access success rate by 3.2%,the load balancing degree by 20%,and the robustness by two orders of magnitude.
基金supported by grants from the Natural Science Foundation of Jiangsu Province(BK20221377 and BK20220607)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(22KJB180023)the National Natural Science Foundation of China Grants(32200783,32350017,and 92368104),and the Qing Lan Project of Jiangsu Province.
文摘Hearing and balance disorders are significant health issues primarily caused by developmental defects or the irreversible loss of sensory hair cells(HCs).ldentifying the underlying genes involved in the morphogenesis and development of HCs is crucial.Our current study highlights rhpn2,a member of rho-binding proteins,as essential for vestibular HC development.The rhpn2 gene is highly expressed in the crista and macula HCs.Loss of rhpn2 function in zebrafish reduces the otic vesicle area and vestibular HC number,accompanied by vestibular dysfunction.Shorter stereocilia and compromised mechanotransduction channel function are found in the crista HCs of rhpn2 mutants.Transcriptome RNA sequencing analysis predicts the potential interaction of rhpn2 with rhoab.Furthermore,co-immunoprecipitation confirms that Rhpn2 directly binds to RhoA,validating the interaction of the two proteins.rhpn2 knockout leads to a decreased expression of rock2b,a canonical RhoA signaling pathway gene.Treatment with the RhoA activator or exogenous rock2b mRNA injection mitigates crista HC stereocilia defects in rhpn2 mutants.This study uncovers the role of rhpn2 in vestibular HC development and stereocilia formation via mediating the RhoA signaling pathway,providing a target for the treatment of balance disorders.
文摘An integral part of the effort to reduce greenhouse gas emissions is carbon footprint accounting.EPA categorizes facility carbon footprints in three scopes.Scope-2 emissions include electricity,heat or steam purchased from a utility provider.This paper evaluates the existing calculation methods for scope-2 CO2 emissions for purchased electricity.The electricity grid in US is complex and is divided spatially into states,eGRID regions,balancing authorities(BAs),and utilities.Up to hourly temporal granularity can be obtained from available datasets.A matrix is developed that categorizes different datasets based on the complexity to calculate the carbon emission factors.Spatial and temporal variations are evaluated.There are significant spatial overlap between regions in different categories and emission factors within a region show sub-regional variation.An area analysis is done using zip-code polygons to determine whether a state or balancing authority is smaller for all the overlapping cases.Temporal variations in emission factors are significant depending on the balancing authority considered.A single method to calculate scope-2 emission factors may not be accurate and efficient in every case and a nuanced assessment of emission factors is warranted.An implementation pathway for a“smart carbon calculator”—one that gives accurate carbon footprint that is the spatially and temporally most granular is suggested.
基金supported by the National Key Research and Development Program of China(Grants No.2024YFF0810500 and 2022YFD1900802)the National Natural Scientific Foundations of China(Grants No.41991232,42301016 and 42571034)the Hainan Provincial Natural Science Foundation of China(Grant No.424QN354).
文摘Accurate water budget closure is critical for sustainable water resource management facing increased pressures from climate change and human activities.Although error reduction methods for individual water balance components have advanced,persistent biases remain due to the independent development of datasets,impacting basin scale water budget balance.In this research,we analyzed the mathematical origin of the bias between water budget components and developed a new basin-scale water balance calibration method that redistributes errors across components while enforcing water balance constraints.Validation confirms systematic improvements,with reduced RMSE(Precipitation:-2.29 mm/month;ET:-1.34 mm/month)and increased R2 against in situ observations.Applied to the Jinghe River Basin(2000−2019),the calibrated data reveal declining precipitation(-1.70 mm/year)and evapotranspiration(-1.84 mm/year)alongside slightly increasing runoff(0.20 mm/year in basin depth),signaling a drying trend.Land cover changes—marked by cropland loss(-3,497 km^(2))and forest(+720 km^(2))and grassland(+2,776 km^(2))expansion—reflect improved water consumption requirements by ecosystem,raising concerns for water retention and ecosystem stability.The method is particularly effective for ungauged basins with sparse ground data and underscores the need for integrated land-water management to enhance long-term resilience.
基金supported by China Southern Power Grid Corporation(036000KC23090005(GDKJXM20231027)).
文摘This paper presents a programmable frequency scan algorithm based on harmonic balance.The core idea involves treating systems under perturbation as nonlinear time-periodic(NTP)systems.Steady-state harmonics are first solved via Newton-Raphson iteration through a set of nonlinear equations,and then input-output variables are selected to estimate the linear transfer function of the original NTP system without perturbations.The applications and insights of the proposed algorithm are discussed,particularly in guiding existing frequency scan algorithms,which are restricted by time-domain signal generation or measurement.This improvement is achieved through linear stability analysis of NTP systems with perturbations.
基金supported by the National Key R&D Plan“Inter-governmental International Science&Technology Innovation Cooperation”Key Specialized Program,China(2025YFE0102800)the Program of the State Key Laboratory of Cryospheric Science and Frozen Soil Engineering,Chinese Academy of Sciences(CSFSE-ZZ-2403).
文摘Tajikistan contains the majority of Central Asia’s glaciers,which cover about 6.00%of the national territory;their rapid shrinkage poses a significant threat to regional water resource security.However,glacier monitoring in Tajikistan was interrupted after 1991,creating a substantial gap in understanding the current state and temporal evolution of these glaciers.Based on glacier inventory data,in situ measurements,and published literature,this study examined the present status and recent variations of glaciers in Tajikistan through data integration and validation,literature collation and comparative analysis,and the application of Geographic Information System(GIS)spatial analysis techniques.As of 2023,Tajikistan possesses a total of 11,528 glaciers,encompassing an area of 7624.48(±305.58)km2.Small glaciers dominate in number,whereas large glaciers account for the majority of the total area.Over the past two decades,the glacier count has decreased by 2014,and the total area has decreased by 628.98 km2,corresponding to an average annual reduction rate of 0.33%.Regional shrinkage rates range from 4.10%to 22.28%.Glaciers have undergone accelerated mass loss during the past 20 a;only those on the northeastern Pamir Plateau exhibit a weak positive mass balance.Observations of typical monitored glaciers also reveal intensified melting and retreat,consistent with regional trends.In light of the recent acceleration of glacier shrinkage in Tajikistan,focused measures should be implemented to strengthen glacier monitoring,enhance public awareness of glacier preservation,and promote the sustainable development and utilization of glacier tourism.These findings bridge the knowledge gap regarding the spatiotemporal dynamics of Tajikistan’s glaciers over recent decades and provide essential data support for regional water resource management.
基金financially supported by the National Natural Science Foundation of China(Nos.52373070,52273071 and U25A20255)the Special Support Plan for High-Level Talents in Zhejiang Province(No.2022R51008)the HZNU scientific research and innovation team project(No.TD2025004).
文摘Rubber-toughened thermoplastic materials have become ubiquitous in modern society owing to their lightweight nature and desirable combination of advantageous performances.Despite the ever-increasing demand,the development of polymer alloys that are lightweight,high-strength,and high-toughness remains an ongoing challenge.Inspired by the unique“salami”microstructure from commercial acrylonitrile butadiene styrene copolymer(ABS)and high-impact polystyrene(HIPS),a facile approach was developed to overcome the trade-off between enhancing the toughness and rigidity of fully polymer-based alloys by virtue of elastomeric salami particles.This strategy entails pre-grafting rigid poly(lactic acid)(PLLA)chains with glycidyl methacrylate-grafted octene ethylene copolymer(POE-g-GMA)using complementary reactive groups.It can be envisaged that the PLLA grafts featuring strong incompatibility with polypropylene(PP)remain fixed in elastomer phase upon the subsequent melt compounding,facilitating the in situ formation of“hard core(PLLA)-soft shell(polyolefin elastomer,POE)”particles in polypropylene(PP)matrix.The all-polymer alloys containing elastomeric salami particles demonstrated unprecedented performance combinations,including upper notched impact strengths(56.8 kJ/m2),even higher tensile strength(36.8 MPa),and Young’s modulus(0.93 GPa)than that of the PP matrix.Furthermore,these materials are lightweight without the incorporation of reinforcing nano-fillers,which is competitive with industrial engineering plastics.It is highly anticipated that this universal and highly efficient protocol will be appropriate for arbitrary rubber toughened/reinforced systems,offering a paradigm in the design of advanced all-polymer alloys.
基金supported by the National Natural Science Foundation of China(Grant Nos.42192551,42150710531).
文摘The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study provides more rigorous evidence supporting the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity(PV)inversion method.Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s^(–1) and 10 m s^(–1),we demonstrate that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component,characterized by vortex Rossby waves.Furthermore,the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core.As an air parcel undergoes cyclonic rotation,it ascends on the right side of the tilt vector,which increases relative humidity,leads to saturation,and drives the development of convective asymmetries,with maximum upward motion aligned with the tilt direction.This study suggests that the response of TC vortices to the environmental VWS involves complex interactions between vortex tilt,asymmetries in TC structure,and convection,all of which can largely be understood within the framework of balanced dynamics.
基金funded by the National Key R&D Program of China,China(No.2024YFF0507903)the National Key Research and Development Program of China(Grant No.2024YFF0507904)the National Natural Science Foundation of China,China(Grant No.52379114).
文摘In-situ enlargement of super-large-span tunnels can intensify excavation-induced unloading in the surrounding rock,increasing deformation demand and failure risk during construction.This study combines laboratory model tests with FLAC3D simulations to evaluate the stabilizing role of prestressed anchor cables and to establish an energy-balance framework for support optimization.Comparative model tests of existing and enlarged tunnel sections,with and without anchors,show that reinforcement increases load-carrying capacity,reduces displacement,and confines damage to more localized zones.The numerical simulations reproduce displacement fields,shear-strain localization,and plastic-zone evolution with good agreement against the experimental observations.The energy framework is implemented in the in-situ simulations by quantifying unloading-related energy release in the rock mass and reinforcement work contributed by the anchors,and by introducing an energy release–reinforcement ratio as a stability indicator.Parametric analyses indicate that anchor length,spacing,and prestress influence stability in a nonlinear manner,with diminishing returns once reinforcement extends beyond the mechanically dominant deformation zone.An efficient parameter window is identified that improves deformation and yielding control while avoiding unnecessary reinforcement.The results provide an energy-consistent and design-oriented basis for prestressed anchorage selection in large-span tunnel expansion.
基金supported by the National Natural Science Foundation of China under Grant No.22505100.
文摘Energetic materials face critical challenges in balancing energy density and safety,driving the development of low-sensitivity high-energy materials.Though vital for modern defense and civilian applications,low-sensitivity high-energy materials remain scarce,with 1,3,5-trinitro-2,4,6-triaminobenzene as the only deployed example.Planar lamellar energetic crystals,which utilize weak interlamellarπ-πstacking for mechanical energy dissipation,have shown significant promise.However,their rational design is constrained by insufficient understanding of intermolecular interaction synergy.This review synthesizes the structural features of planar lamellar energetic crystals,emphasizing three core elements:the single-atomic-thickness planar stacking architecture,the"strong intralamellar and weak interlamellar interaction"paradigm(key to balancing energy density and safety for low-sensitivity high-energy materials,LSHEMs),and the role of molecular planarity in reducing shear slip barriers.It categorizes design strategies into two frameworks:H–bonding dominated(single-component:cross-shaped assembly,strong H–bonding in high symmetric molecules;multi-component methods:tenon-and-mortise,acceptor-donor separation)and other intermolecular interactions(e.g.,π-πstacking-drivenπ-π2max model,π-hole recognition).Case studies in single/multi-component crystals confirm that these strategies tune interaction synergy to achieve target packing motifs.The review highlights that interaction engineering is pivotal for PLEC design,offering a targeted theoretical framework for rational development of LSHEMs(to address the scarcity of practical LSHEMs)and guiding future crystal engineering for energy-safety balanced systems.
基金Chongqing Education Science Planning Project.Project Name:Research on Talent Training of Community Rehabilitation Major in Higher Vocational Colleges Based on OBE Concept(Project No.:K23ZG3420222)。
文摘Objective:To analyze the improvement effect of early postoperative rehabilitation training on balance ability and quality of life in elderly patients with hip fracture.Methods:A total of 50 elderly patients with hip fracture admitted to our hospital from January 2023 to January 2024 were selected and divided into the observation group(25 cases)and the control group(25 cases)by random number table method.The control group received routine nursing,while the observation group received early rehabilitation training on the basis of routine nursing.The balance ability(Berg Balance Scale,BBS)and quality of life(SF-36)of the two groups were compared.Results:The BBS scores of the observation group at all postoperative time points were significantly higher than those of the control group(p<0.05),and the quality-of-life scores of the observation group were also significantly higher than those of the control group(p<0.05).Conclusion:Early postoperative rehabilitation training for elderly patients with hip fracture can improve their balance ability,enhance their quality of life,and reduce the incidence of postoperative complications,which is worthy of clinical promotion.
基金supported by the National Natural Science Foundation of China(Grant Nos.12172267 and 12302014).
文摘Quasi-periodic solutions with multiple base frequencies exhibit the feature of 2π-periodicity with respect to each of the hyper-time variables.However,it remains a challenge work,due to the lack of effective solution methods,to solve and track the quasi-periodic solutions with multiple base frequencies until now.In this work,a multi-steps variable-coefficient formulation is proposed,which provides a unified framework to enable either harmonic balance method or collocation method or finite difference method to solve quasi-periodic solutions with multiple base frequencies.For this purpose,a method of alternating U and S domain is also developed to efficiently evaluate the nonlinear force terms.Furthermore,a new robust phase condition is presented for all of the three methods to make them track the quasi-periodic solutions with prior unknown multiple base frequencies,while the stability of the quasi-periodic solutions is assessed by mean of Lyapunov exponents.The feasibility of the constructed methods under the above framework is verified by application to three nonlinear systems.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62331024 and 62571549)the National Key Research and Development Program of China(Grant No.2022YFB2802804)。
文摘Rydberg-atom-based superheterodyne receivers integrate self-calibration,high sensitivity,a wide operational frequency range,and phase/frequency resolved detection capabilities,demonstrating broad application prospects as nextgeneration microwave receivers.Linear gain and linear dynamic range(LDR)are critical metrics for assessing receiver sensitivity and demodulation fidelity,respectively.We numerically solve the four-level master equation and then employ particle swarm optimization(PSO)algorithm to co-optimize linear gain and LDR in atomic superheterodyne receivers based on balanced homodyne detection.Further,we systematically account for dominant dephasing mechanisms in the simulation,encompassing spontaneous decay,transit dephasing,collision dephasing,laser linewidth dephasing,and Doppler averaging.Homodyne readout utilizes both the real and imaginary parts of polarizability for sensing.In the case of the photon shot noise limit,its signal-to-noise ratio(SNR)expression resembles that of direct optical-intensity readout.However,the inherent coherent subtraction operation in homodyne detection significantly suppresses common-mode noise,while appropriately increasing the reference beam power enhances the gain in practical experiments.Indeed,this co-optimization problem,characterized by a high-dimensional variable space,two objectives,and non-convexity,is well-suited for solution by PSO.In addition,probe and coupling detuning contribute equivalently to polarizability and compensate for each other owing to Doppler averaging,thereby reducing the optimization variable space by one.By adopting a product form of linear gain and LDR as the fitness function,the PSO achieves rapid convergence.Here,the effectiveness of the PSO results is verified via the total harmonic distortion(THD).The relative error-based LDR calculation method we proposed efficiently measures receiver response linearity with consuming fewer computational resources.This research is expected to offer valuable insights into enhancing the performance of Rydberg-atom-based superheterodyne receivers.
